1. Technical Field
The present invention relates to vaccine immunotherapy. More specifically, the present invention relates to compositions and methods for eliciting an immune response to endogenous or exogenous peptide or protein antigens in patients having cancer or other antigen-producing disease states or lesions.
2. Background Art
It has become increasingly apparent that human cancers possess antigens, which, if acted upon by the host's immune system, can result in tumor regression. These antigens have been defined by both serological and cellular immune approaches, which have led to the definition of both B and T cell epitopes (Sahin, 1997; Van der Eynde, 1997; Wang, 1999). Based upon these results, it has become a goal of cancer immunotherapists to induce the regression of tumors. However, historically, successful efforts have been sporadic and generally minor in frequency and magnitude.
A fundamental problem in the effort to immunize cancer patients, i.e., against tumor antigens, is that the tumor-bearing state is associated with immunosuppressive mechanisms derived from both the tumor and the host's disturbed immune system (Kavanaugh, 1996), thereby making immunization difficult and until now impossible on a consistent basis. Immune suppression or depletion involves a reduced capacity of the immune system to respond. Such suppression can be drug-induced, i.e., by drug treatment, virus-induced, e.g., as in AIDS, or induced by a disease state such as cancer. The immune system in this condition is effectively turned off. In the case of a disease state such as cancer, the body is not able to protect itself against tumor antigens, thus allowing a tumor to grow and possibly metastasize.
A variety of tumor immunization strategies have been developed. All of these strategies are complex and deviate significantly from the conventional immunization strategies used for infectious diseases (see, e.g., Weber, 2000). One such tumor immunization strategy involves Theratope®, a sialyl Tn polysaccharide mucin antigen conjugated with keyhole limpet hemocyanin (KLH) and administered with Detox® mycobacterium adjuvant and low dose cyclophosphamide (Maclean, 1996). Use of this vaccine in patients with metastatic breast and ovarian cancer has yielded major clinical responses (i.e., greater than 50% tumor reduction) in only a low percentage of patients.
Gene therapy has also been attempted using viral constructs as expression vectors for genes expressing tumor antigens. For example, a recombinant vaccinia virus construct encoding modified forms of human papilloma virus (HPV) E6 and E7 protein sequences has been used for immunization of patients with cervical cancer. Vaccination with this construct yielded questionable clinical responses (Borysiewickz, 1996). See also, Sanda, 1999 wherein a recombinant vaccinia-PSA (prostate-specific antigen) construct was used as a vaccine in prostate cancer patients.
Another approach has been dendritic cell-mediated therapy, e.g., wherein dendritic cells were pulsed with oligopeptide fragments of prostate-specific membrane antigens (PSMA). The dendritic cells (with or without the priming PSMA antigens) were then administered to patients with metastatic prostate cancer. Major clinical responses were obtained in only a low percentage of patients (Murphy, 1999; see also, Tjoa, 2000).
Additionally, autologous tumors have been used with low dose cyclophosphamide and BCG (Bacillus Calmette-Guerin) to immunize cancer patients with malignant melanoma. However, few clinical responses were reported (Mastrangelo, 1996). Another strategy included using MAGE antigens with a variety of vaccine adjuvants. Again, this has yielded few, if any, responses in patients with malignant melanoma (personal communication, Thierry Boon).
Several patents to Doyle et al (U.S. Pat. Nos. 5,503,841; 5,800,810; 6,060,068; 5,643,565; and 5,100,664) disclose methods of enhancing the immune response in patients using interleukin 2 (IL-2). This method is disclosed for use in response to infectious diseases and primarily functions using antigens known to be immunogenic. Limited applicability was demonstrated. As disclosed above, the treatment of cancer is known to require different approaches. To date, treatment with IL-2 has shown minor effects in two cancers, renal cell and malignant melanoma (response rates less than 20%). It is generally considered ineffective in squamous cell head and neck and cervical cancer and in prostate cancer. Hence, it is not approved for these uses.
It is important to contrast prevention using known “classic” antigens of complex structure and high molecular weights in healthy patients vs. treatment (generally unsuccessful) with tumor antigens or peptides (general unsuccessful) in immunosuppressed patients (generally unsuccessful). The first is easy and our current viral vaccines attest to their efficacy. The latter is nearly impossible on a routine basis despite thirty years of intense effort.
Moreover, effective cancer vaccines require stimulation of cell-mediated immunity, perhaps even in preference to antibody production. As noted, despite numerous studies with various antigens, adjuvants and vaccine constructs, the clinical trial data to date have been disappointing. The critical events for a T cell mediated anti-cancer immune response are antigen presentation to T cells, primarily in the lymph nodes draining the site of the tumor or immunization, followed by T cell activation and migration to the peripheral sites. In fact, the uptake of the antigen by tissue macrophages, neutrophils and/or dendritic cells and presentation of processed peptides in combination with MHC class I and class II antigens to the T cells in the lymph node are crucial to a complete immune response. Key to a successful T cell immune activation is the generation of the appropriate cytokine environment to drive the immune response to a vaccine, at both the site of immunization and draining lymph nodes.
The kinetics of the immune response includes two phases. The first is the draining of the antigen and soluble proteins to the lymph nodes, where an initial immune activation occurs. Twenty four to forty eight hours later, antigen-presenting cells (APCs), most particularly dendritic cells, migrate from the site of immunization via the draining lymphatic ducts to the lymph node, where a second wave of presentation of antigen and activation occurs. More specifically, the APCs interact in the lymph node with precursor T helper cells via engagement of co-stimulatory receptors as well as T cell receptors to yield T helper 1 (Th1) cells and/or T helper 2 (Th2) cells. The ratio of these subsets controls subsequent development of either cell-mediated or humoral (antibody) immune responses (Th1 biasing towards DTH/cytotoxicity, whereas Th2 biases towards antibody production). Following the induction of these activated T cells, the immune response subsides, leaving predominately memory T cells, which are capable of responding upon re-exposure to antigen.
The critical events in this pathway are mediated by cytokines that bias the response in the direction of humoral or cellular immunity. Locally produced cytokines, such as IL-1, IL-2, IFN γγ, GM-CSF, IL6, TNF-α, IL-12 and IL-8, are associated with the recruitment of immune system cells, antigen uptake, dendritic cell maturation, dampening of T regulatory cell activity, T cell education and proliferation, and the development of Th1 cells (Naylor, 2003). The interdependence of the response means that the activity of any given cytokine depends on the occurrence of precursor events such that the simultaneous presence of multiple cytokines can have different effects at both the injection site and the draining lymph nodes, depending on the kinetics of cell responses to different cytokines.
The present invention utilizes the natural cytokine mixture (NCM) as disclosed in U.S. Pat. Nos. 5,632,983 and 5,698,194, issued to Applicant, to immunize patients, such as cancer patients or other patients with other antigen-producing lesions or disease states. More specifically, NCM (also referred to herein as IRX-2) has been previously shown in U.S. Pat. No. 5,698,194 to be effective in promoting T cell development and function in aged, immunosuppressed mice. NCM was shown to decrease the proportion of immature T cells and increase the proportion of mature T cells in the thymus. The NCM included IL-1, IL-2, IL-6, IL-8, IL-12, IFN-γ, TNF-α, GM-CSF, G-CSF, and IL-3, IL4, IL-7 in trace amounts.
It will be apparent from the disclosure detailed herein that the cytokine compositions of the invention and the methods that utilize them are applicable to the stimulation of an immune response to any antigen of interest, e.g., cancer or tumor antigens, as well as antigens produced by other persistent disease states or lesions. As detailed herein, the cytokine mixture of the invention acts as an adjuvant preferably to stimulate T cell immunity in vivo.
Moreover, the present invention relates to, but not exclusively to, eliciting an immune response to either endogenous antigens, i.e., proteins or peptides that are located in vivo and are processed and presented by APCs (such as dendritic cells) in vivo, or to exogenous antigens, i.e., proteins or peptides that have been isolated or generated in vitro and then administered in vivo to an environment (e.g., a lymph node) where dendritic cells are present and can effectively present the antigens, e.g., to T cells. In particular as it relates to peptide antigens, this goal is considered by many immunologists to be insurmountable. Peptides are generally considered to be much too small to be effective immunogens, their half life is short, and they are often non-mutated self antigens to which the patient is immunologically tolerant. Thus, gaining an immune response to such antigens is tantamount to inducing auto-immunity.
As described herein, the present invention is useful to develop a consistent and effective method of vaccine immunotherapy, wherein immune responses are elicited in patients, such as cancer patients, using the cytokine compositions of the present invention in combination with endogenous and/or exogenous disease-associated antigens, including tumor antigens and peptides.